Endoplasmic Reticulum Diagram | Structure of Rough and Smooth ER

Structure and function of endoplasmic reticulum is important for the cell to carry out its proper functioning. An excellent way to learn about structure is from diagram. 

What is endoplasmic reticulum?

Endoplasmic reticulum stands for "endoplasm" meaning “the inner portion of cytoplasm” and "reticulum" meaning “network”. The Endoplasmic reticulum was first detected in the cell by Garnier in 1897. Under a microscope, there is a network of interconnected membrane-bounded channels extending from the cell membrane to the nuclear envelope.

Structure and function of Endoplasmic reticulum

The Endoplasmic reticulum is a network of flattened membrane-bounded sacs called cisternae which separates the inner content of channels from cytoplasmic materials. The endoplasmic reticulum can be distinguished into two forms based on appearance and function.

  1. Rough Endoplasmic Reticulum
  2. Smooth Endoplasmic Reticulum

structure and function of endoplasmic reticulum
Structure of endoplasmic reticulum. The image created in BioRender.com

1. Structure of rough endoplasmic reticulum

Rough Endoplasmic Reticulum also abbreviated as RER is named for its rough appearance due to the attached ribosomes. The RER resides adjacent to the nucleus of the cell, and its membrane is continuous with the nuclear envelope's outer membrane. 

The ribosomes on the rough ER are specialized in protein synthesis and proteins after synthesis is stored in the cytoplasm or transported out of the cell through these channels to the Golgi apparatus.

Functions of rough endoplasmic reticulum

The main funtions of RER are:
  • The proteins synthesized in RER are folded, tagged with a signal sequence, and packed into transport vesicles by the Golgi apparatus and sent to the destination.
  • Integral membrane proteins are synthesized in RER.

2. Structure of smooth endoplasmic reticulum

Smooth Endoplasmic Reticulum abbreviated as SER has a smooth surface due to the absence of ribosomes. It plays an essential role in the transport of materials from one side of the cell to the other side.

Functions of smooth endoplasmic reticulum

The main functions of SER are:
  • SER is involved in the metabolism of different substances especially lipids, cholesterol, and phospholipid.
  • It detoxifies harmful chemicals and drugs in liver cells.
  • In muscle and nerve cells, SER play important role in the transmission of nerve signals.
  • It stores and releases calcium ions.

Video Lesson

Some question and answer

Q. What is the difference between smooth and rough endoplasmic reticulum?
A. Rough endoplasmic reticulum has ribosomes attached to it while smooth endoplasmic reticulum does not contain ribosomes.

Q. What is the function of rough endoplasmic reticulum?
A. Rough endoplasmic reticulum is involved in the synthesis and transport of proteins and enzymes.

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